Circuit apparatus, oscillator, electronic instrument, and vehicle

ABSTRACT

A circuit apparatus includes an oscillation circuit that causes a resonator to oscillate to produce an oscillation signal, an oven control circuit that controls a heater provided in correspondence with the resonator, a non-volatile memory that stores control data, a holding circuit that holds the control data transferred from the non-volatile memory, and a processing circuit that carries out a process based on the control data held in the holding circuit. After a power source voltage is supplied, the processing circuit carries out the process of transferring the control data from the non-volatile memory to the holding circuit, and after the transfer of the control data is completed, the processing circuit causes based on a data transfer end signal the oven control circuit to start operating.

The present application is based on, and claims priority from JPApplication Serial Number 2019-168936, filed Sep. 18, 2019, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a circuit apparatus, an oscillator, anelectronic instrument, a vehicle, and the like.

2. Related Art

There has been a known oscillator called an OCXO (oven controlledcrystal oscillator). An OCXO is used as a reference signal source, forexample, in a base station, a network router, and a measurementinstrument. For example, JP-A-2017-123552 discloses an OCXO using atemperature sensor provided outside a circuit apparatus to improve thetemperature resolution of temperature detection data.

Digital signal processing in an OCXO, such as temperature compensation,can be performed, for example, by using data transferred from a memoryto a register at the time of activation of the OCXO. Immediately afterthe start of oven control in the OCXO, however, the current consumed bya heater abruptly increases in some cases depending on the temperaturearound the heater, and a voltage drop due to the abrupt increase in theconsumed current temporarily unstabilizes the power source voltage. Onthe other hand, the amount of data transferred from the memory to theregister at the time of the activation increase as the digital signalprocessing advances, and the increase in the amount of data undesirablyprolongs the data transfer period. Therefore, when the abrupt increasein the current consumed by the heater unstabilizes the power sourcevoltage in the long data transfer period, a data transfer error andother problems occur.

SUMMARY

An aspect of the present disclosure relates to a circuit apparatusincluding an oscillation circuit that causes a resonator to oscillate toproduce an oscillation signal, an oven control circuit that controls aheater provided in correspondence with the resonator, a non-volatilememory that stores control data, a holding circuit that holds thecontrol data transferred from the non-volatile memory, and a processingcircuit that carries out a process based on the control data held in theholding circuit. After a power source voltage is supplied, theprocessing circuit carries out the process of transferring the controldata from the non-volatile memory to the holding circuit, and after thetransfer of the control data is completed, the processing circuit causesbased on a data transfer end signal the oven control circuit to startoperating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of the configuration of a circuit apparatusaccording to an embodiment of the present disclosure.

FIG. 2 shows an example of the detailed configuration of the circuitapparatus according to the present embodiment.

FIG. 3 shows an example of the contents stored in a register and a RAM.

FIG. 4 shows an example of signal waveforms that describe the action ofthe circuit apparatus according to the present embodiment.

FIG. 5 describes the action of the circuit apparatus according to thepresent embodiment.

FIG. 6 shows an example of the configuration of an oven control circuit.

FIG. 7 shows an example of the configuration of a heater.

FIG. 8 shows an example of the configuration of an operationalamplifier.

FIG. 9 shows an example of the structure of an oscillator.

FIG. 10 shows an example of the configuration of an electric instrument.

FIG. 11 shows an example of the configuration of a vehicle.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An embodiment of the present disclosure will be described below. It isnot intended that the present embodiment described below unduly limitsthe contents set forth in the appended claims. Further, allconfigurations described in the present embodiment are not necessarilyessential configuration requirements.

1. Circuit Apparatus

FIG. 1 shows an example of the configuration of a circuit apparatus 20according to the present embodiment. The circuit apparatus 20 includesan oscillation circuit 30, which causes a resonator 10 to oscillate, anoven control circuit 40, a processing circuit 50, a non-volatile memory70, and a holding circuit 80. The circuit apparatus 20 is an integratedcircuit (IC) manufactured, for example, in semiconductor processes andis, for example, a semiconductor chip in which circuit elements areformed on a semiconductor substrate. An oscillator 4 according to thepresent embodiment includes the resonator 10 and the circuit apparatus20. The oscillator 4 further includes a heater 2. The resonator 10 iselectrically coupled to the circuit apparatus 20. The resonator 10 iselectrically coupled to the circuit apparatus 20, for example, by usinginternal wiring lines, bonding wires, or metal bumps in a package thataccommodates the resonator 10 and the circuit apparatus 20.

The resonator 10 is a device that produces mechanical vibration inresponse to an electric signal. Specifically, the resonator 10 is aresonator built in an oven controlled crystal oscillator (OCXO)including a thermostatic chamber. The resonator 10 can be achieved, forexample, by a resonator element, for example, a quartz crystal resonatorelement. For example, the resonator 10 can be achieved by a quartzcrystal resonator that undergoes thickness slide resonance, such as aquartz crystal resonator cut at an AT cut angle or an SC cut angle. Theresonator 10 in the present embodiment can be achieved by any of avariety of resonator elements, for example, a resonator element of typeother than the thickness slide resonance type and a piezoelectricresonator element made of a material other than quartz crystal. Forexample, the resonator 10 may be a SAW (surface acoustic wave) resonatoror a MEMS (micro electro mechanical systems) resonator in the form of asilicon resonator formed by using a silicon substrate.

The oscillation circuit 30 causes the resonator 10 to oscillate toproduce an oscillation signal OSCK. For example, the oscillation circuit30 is electrically coupled to the resonator 10 via resonator couplingpads T1 and T2 of the circuit apparatus 20 and produces the oscillationsignal OSCK by causing the resonator 10 to oscillate. For example, theoscillation circuit 30 drives the resonator 10 via signal lines L1 andL2 coupled to the pads T1 and T2 to cause the resonator 10 to oscillate.The oscillation circuit 30 includes a drive circuit and other componentsfor oscillation that are provided between the pads T1 and T2. Forexample, the oscillation circuit 30 can be achieved by a transistor,such as a bipolar transistor that achieves the drive circuit, andpassive elements, such as a capacitor and a resistor. The drive circuitis a core circuit of the oscillation circuit 30, and the drive circuitdrives the resonator 10 based on current or voltage to cause theresonator 10 to oscillate. The oscillation circuit 30 can be any of avariety of types of oscillation circuit, for example, a pierce-typeoscillation circuit, a Colpitts-type oscillation circuit, aninverter-type oscillation circuit, or a Hartley-type oscillationcircuit. The oscillation circuit 30 may be provided with a variablecapacity circuit, and the oscillation frequency of the oscillationcircuit 30 may be adjustable by adjustment of the capacity of thevariable capacity circuit. The variable capacity circuit can be achievedby a variable capacity device, such as a varactor. It is noted that thecoupling in the present embodiment is electrical coupling. Theelectrical coupling refers to coupling that allows transmission of anelectric signal and hence transmission of information carried by theelectric signal. The electrical coupling may be coupling via an activeelement or any other component.

The oven control circuit 40 controls the heater 2 provided incorrespondence with the resonator 10. For example, the oven controlcircuit 40 performs oven control on the resonator 10, which is anoven-type resonator including a thermostatic chamber. That is, the ovencontrol circuit 40 controls the heater 2 to control the temperature ofthe thermostatic chamber that is an oven in which the resonator 10 isprovided. The thermostatic chamber may be of single oven type or doubleoven type. Specifically, the oven control circuit 40 controls heatgeneration performed by the heater 2 based on the result of temperaturedetection performed by an oven-control temperature sensor provided incorrespondence with the resonator 10. The temperature sensor isprovided, for example, outside the circuit apparatus 20. A temperaturesensor provided in the circuit apparatus 20 may instead be used. Forexample, the oven control circuit 40 outputs an oven control signal VOV,which is a voltage signal for oven control, to the heater 2 to controlthe temperature of the heat generated by the heater 2. The oven controlsignal VOV, which is a heater control signal, is outputted via a pad T3to the heater 2, which is provided outside the circuit apparatus 20. Theoven control circuit 40 then performs temperature adjustment in such away that an oven temperature that is the temperature of the thermostaticchamber is equal to a set temperature. The heater 2 is, for example, aheat generator for adjusting the oven temperature. The heater 2 isprovided in correspondence with the resonator 10 and is provided at alocation corresponding to the resonator 10. Specifically, the heater 2is disposed along with the resonator 10 in the thermostatic chamber. Forexample, the heater 2 is disposed in the vicinity of the resonator 10.

The non-volatile memory 70 is a nonvolatile-type memory that stores avariety of types of information. Specifically, the non-volatile memory70 stores control data DCN. The control data DCN is data for controllingthe circuit apparatus 20 and is also data for a variety of settings forcontrol and action of the circuit apparatus 20. The holding circuit 80is a circuit that temporarily stores a variety of types of information.Specifically, the holding circuit 80 holds the control data DCNtransferred from the non-volatile memory 70. That is, the holdingcircuit 80 temporarily stores the control data DCN. The non-volatilememory 70 can, for example, be an EEPROM (Electrically ErasableProgrammable Read-Only Memory), which can electrically delete data, oran OTP (One Time Programmable) memory, for example, using an FAMOS(Floating gate Avalanche injection MOS). The non-volatile memory 70 mayinstead be a memory using a fuse cell. The holding circuit 80 can beachieved by a register 82 and a RAM 84 as shown in FIG. 2, which will bedescribed later.

The processing circuit 50 performs a variety of types of processing.Specifically, the processing circuit 50 performs processing based on thecontrol data DCN held by the holding circuit 80. For example, theprocessing circuit 50 performs processing for controlling each of thecircuits of the circuit apparatus 20 and digital signal processing, suchas temperature compensation and digital filtering. The processingcircuit 50 can be achieved, for example, by an ASIC (ApplicationSpecific Integrated Circuit) achieved by automatically routed wiring,such as a gate array. The processing circuit 50 may instead be achievedby a CPU, a DSP, or any other processor.

In the present embodiment, the processing circuit 50 carries out theprocess of transferring the control data DCN from the non-volatilememory 70 to the holding circuit after the power source voltage issupplied to the processing circuit 50, and when the transfer of thecontrol data DCN is completed, the processing circuit 50 causes the ovencontrol circuit 40 to start operating. Specifically, the processingcircuit 50 causes the oven control circuit 40 to start operating basedon a data transfer end signal TEND in FIG. 2, which will be describedlater. That is, when the data transfer end signal TEND becomes active,the processing circuit 50 causes the oven control circuit 40 to startoperating. For example, when the power source voltage is supplied to thecircuit apparatus 20, the processing circuit 50 instructs transfer ofthe control data DCN from the non-volatile memory 70 to the holdingcircuit 80. For example, when the circuit apparatus 20 is powered on sothat power-on reset state is canceled, the processing circuit 50instructs the transfer of the control data DCN. The control data DCNstored in the non-volatile memory 70 is thus read and transferred to theholding circuit 80. After the control data DCN is transferred to andheld in the holding circuit 80, the processing circuit 50 instructs theoven control circuit 40 to start operating. The oven control circuit 40is thus activated and controls the heater 2. That is, the oven controlcircuit 40 outputs the oven control signal VOV according to the resultof the temperature detection performed by the temperature sensor tocontrol the temperature of the thermostatic chamber in which theresonator 10 is provided. For example, the temperature control is soperformed that the temperature of the thermostatic chamber falls withina fixed range.

For example, at the time of activation of the oven control, the currentto be consumed by the heater 2 abruptly flows to the heater 2, resultingin variation in power source voltage VDD supplied to the circuitapparatus 20 and variation in power source voltage GND, that is,resulting in unstable power source voltages. When the control data DCNis transferred from the non-volatile memory 70 to the holding circuit 80in such an unstable power source voltage state, a data transfer errorand other problems could occur. For example, when the processing circuit50 performs the digital signal processing, such as the temperaturecompensation in the OCXO, the amount of control data DCN transferredfrom the non-volatile memory 70 to the holding circuit 80 increases, andthe data transfer period lengthens accordingly. For example, when theamount of control data DCN is several hundreds of bits, the length ofthe data transfer period is about several microseconds, whereas whenhigh-precision data signal processing is performed, the length of thedata transfer period becomes several milliseconds or longer. Therefore,when the power source voltage becomes unstable in such a long datatransfer period, a data transfer error occurs, undesirably resulting ina situation in which incorrect control data DCN is transferred. When thecircuit apparatus 20 is controlled or digital signal processing isperformed based on such incorrect control data DCN, the circuitapparatus 20 malfunctions, the digital signal processing, such as thetemperature compensation, is performed incorrectly, or other problemsoccur.

In this regard, in the present embodiment, the oven control circuit 40does not start operating immediately after the power source voltage issupplied, but the control data DCN is transferred from the non-volatilememory 70 to the holding circuit 80 before the oven control circuit 40starts operating. After the transfer of the control data DCN to theholding circuit 80 is completed, the processing circuit 50 instructs theoven control circuit 40 to start operating, and the oven control circuit40 starts controlling the heater 2. In this way, the oven controlcircuit 40 does not start operating in the data transfer period in whichthe control data DCN is transferred from the non-volatile memory 70 tothe holding circuit 80, so that no oven control in which the heater 2 iscontrolled is performed, preventing the unstable power source voltagedue to an abrupt increase in the current consumed by the heater 2. Thesituation in which an unstable power source voltage in the data transferperiod causes incorrect control data DCN to be transferred to theholding circuit 80 can therefore be suppressed. That is, the transfer ofthe control data DCN can be completed before the power source voltagebecomes unstable due to abrupt current consumption in the heater 2,whereby a risk of incorrect data transfer can be reduced. For example,since several seconds are necessary before proper oven feedback controlis performed, waiting for the end of the data transfer period of aboutseveral milliseconds results only in very small adverse effects.

FIG. 2 shows an example of the detailed configuration of the circuitapparatus 20. The circuit apparatus 20 according to the presentembodiment does not necessarily have the configuration shown in FIG. 2,and a variety of variations are conceivable, that is, part of thecomponents in the configuration can be omitted, or another component canbe added to the configuration. The circuit apparatus 20 may be provided,for example, with a temperature sensor and an A/D conversion circuitthat converts a temperature detection voltage from the temperaturesensor from an analog form into a digital form.

The circuit apparatus 20 includes a power-on reset circuit 24. Thepower-on reset circuit 24, to which the power source voltage VDD isexternally supplied via a pad T5, which is a power source terminal,outputs a power-on reset signal XPOR. The power source voltage VDD isalso supplied to the heater 2. The power source voltage GND is inputtedto the circuit apparatus 20 via a pad T6, which is a GND terminal, andsupplied to each of the circuits provided in the circuit apparatus 20.For example, the power source voltage VDD is inputted via an externalconnection terminal of the oscillator 4 and supplied to the circuitapparatus 20 and the heater 2. The power source voltage GND is alsosupplied to the heater 2. The power-on reset circuit 24, to which thepower source voltage VDD is supplied, then changes the level of thepower-on reset signal XPOR from a level L to a level H when the powersource voltage VDD becomes greater than or equal to a given voltage to,for example, cancel the reset state of the processing circuit 50. Theletter “X” of the power-on reset signal XPOR means the negative logic,and when the power-on reset signal XPOR has the level L, the processingcircuit 50 operates in the reset state, and when the level of thepower-on reset signal XPOR changes to the level H, the reset state iscanceled. The processing circuit 50 thus starts operating and instructs,for example, the transfer of the control data DCN from the non-volatilememory 70 to the holding circuit 80. Specifically, the processingcircuit 50 outputs a transfer start signal TSTA to the non-volatilememory 70 to instruct the non-volatile memory 70 to start transferringthe control data DCN.

The circuit apparatus 20 further includes an amplitude detection circuit22. The amplitude detection circuit 22 detects the amplitude of theoscillation signal OSCK from the oscillation circuit 30. The amplitudedetection circuit 22 can be achieved, for example, by a peak detectioncircuit that detects and holds a peak of the oscillation signal OSCK.After the action of the oscillation circuit 30 is enabled, and when theamplitude detection circuit 22 detects that the amplitude of theoscillation signal OSCK exceeds a predetermined value, the amplitudedetection circuit 22 makes a detection signal DET active. For example,the amplitude detection circuit 22 changes the level of the detectionsignal DET from the level L to the level H. When the amplitude detectioncircuit 22 detects that the amplitude of the oscillation signal OSCKexceeds the predetermined value, the processing circuit 50 carries outthe process of starting transfer of the control data DCN from thenon-volatile memory 70 to the holding circuit 80. For example, after thepower-on reset signal XPOR cancels the reset state, and when theamplitude of the oscillation signal OSCK exceeds the predetermined valueso that the detection signal DET from the amplitude detection circuit 22is made active, the processing circuit 50 makes the transfer startsignal TSTA active to instruct transfer of the control data DCN from thenon-volatile memory 70 to the holding circuit 80.

The circuit apparatus 20 further includes a clock signal output circuit90. The clock signal output circuit 90, to which the oscillation signalOSCK is inputted from the oscillation circuit 30, outputs a clock signalCLK based on the oscillation signal OSCK to an external component via apad T4, which is a clock output terminal. The clock signal CLK isoutputted to a component external to the oscillator 4, for example, viathe external connection terminal of the oscillator 4. The clock signaloutput circuit 90 includes a frequency adjustment circuit 92 and abuffer circuit 94. The frequency adjustment circuit 92 adjusts thefrequency of the oscillation signal OSCK and produces the clock signalCLK having a desired frequency. The buffer circuit 94 buffers theproduced clock signal CLK and outputs the clock signal CLK to theexternal component via the pad T4.

The frequency adjustment circuit 92 can be achieved, for example, by afractional-N-type PLL circuit. The fractional-N-type PLL circuitcompares in terms of phase a reference clock signal that is theoscillation signal OSCK with a feedback clock signal that is a clocksignal outputted from the fractional-N-type PLL circuit and divided by adivider circuit. A delta-sigma modulation circuit is then used to set adecimal division ratio. The fractional-N-type PLL circuit is thusachieved. Thereafter, for example, the processing circuit 50 carries outthe process of setting division ratio data set in the fractional-N-typePLL circuit, which is the frequency adjustment circuit 92, based on thetemperature compensation data to achieve the temperature compensation.Setting the division ratio data further allows the frequency of theclock signal CLK to be set at a desired frequency required by anapplication. The buffer circuit 94 is a circuit that buffers the clocksignal CLK and outputs the buffered clock signal CLK to the externalcomponent. The signal format of the outputted clock signal CLK may bethe single-ended CMOS signal format. The signal format may instead beany other signal format, such as LVDS (Low Voltage DifferentialSignaling), PECL (Positive Emitter Coupled Logic), HCSL (High SpeedCurrent Steering Logic), and differential CMOS (Complementary MOS).Still instead, a desired signal format may be selected from the signalformats described above.

The processing circuit 50 includes a digital signal processing circuit52, which performs digital signal processing. The digital signalprocessing circuit 52 operates as a DSP (Digital Signal Processor) andperforms the digital signal processing including, for example, thetemperature compensation performed on the oscillation frequency of theresonator 10. The digital signal processing circuit 52 further performsdigital filtering as the digital signal processing. The digital signalprocessing circuit 52 performs, for example, FIR (Finite ImpulseResponse), IIR (Infinite Impulse Response), and other types of digitalfiltering. The digital signal processing circuit 52 may further performdigital signal processing for aging correction. For example, the digitalsignal processing circuit 52 performs Kalman filtering as the digitalsignal processing for aging correction. The digital signal processingcircuit 52 may perform neural networking as the digital signalprocessing. For example, the digital signal processing circuit 52performs AI-based (Artificial-Intelligence-based) neural networking thatestimates the temperature of the resonator 10 based on the result of thetemperature detection performed by the temperature sensor providedoutside the circuit apparatus 20 or the temperature sensor providedinside the circuit apparatus 20.

The processing circuit 50 further includes an activation control circuit54 and a transfer control circuit 56. The activation control circuit 54controls activation of the oven control circuit 40. That is, theactivation control circuit 54 controls a sequence in accordance withwhich the oven control circuit 40 is activated. For example, theactivation control circuit 54 outputs an oven control start signal STOVto the oven control circuit 40 to control the activation of the ovencontrol circuit 40. The transfer control circuit 56 controls transferassociated with the non-volatile memory 70. That is, the transfercontrol circuit 56 controls the transfer of the control data DCN fromthe non-volatile memory 70 to the holding circuit 80. For example, theactivation control circuit 54 outputs the transfer start signal TSTA tothe non-volatile memory 70 to control the transfer of the control dataDCN. The activation control circuit 54 and the transfer control circuit56 will be described later in detail.

The holding circuit 80 includes a register 82 and a RAM 84. The register82 holds a variety of data for setting the action of the circuitapparatus 20 as the control data DCN. For example, the control datacontains action control data for controlling the action of theoscillation circuit 30 and digital signal processing data used in thedigital signal processing. The register 82 holds the action controldata. The register 82 can be achieved, for example, by flipflopcircuits. The RAM 84 is a memory that stores the variety of data as thecontrol data DCN and can be achieved, for example, by an SRAM. Forexample, the RAM 84 holds the digital signal processing data. That is,the RAM 84 holds as the control data DCN the digital signal processingdata used in the digital signal processing performed by the digitalsignal processing circuit 52. The oscillation circuit 30 can thus be socontrolled as to start the oscillation action by using the actioncontrol data, which is control data on the action of the oscillationcircuit 30 and which is transferred from the non-volatile memory 70 tothe register 82. Specifically, the processing circuit 50 makes anoscillation start signal STOS to be outputted to the oscillation circuit30 active to cause the oscillation circuit 30 to start the oscillationaction. After the oscillation circuit 30 thus starts the oscillationaction using the resonator 10 and produces the oscillation signal OSCK,the digital signal processing data transferred from the non-volatilememory 70 to the RAM 84 can be used to allow the digital signalprocessing circuit 52 to perform the digital signal processing, such asthe temperature compensation.

FIG. 3 shows an example of the contents stored in the register 82 andthe RAM 84. The register 82 stores, for example, the action controldata, such as oscillation enable data, oven control enable data, andoutput enable data, as the control data DCN, as shown in FIG. 3. Theregister 82 further stores frequency adjustment data as the control dataDCN. The oscillation enable data is bit data that enables and disablesthe oscillation circuit 30 to operate and is also the action controldata on the action of the oscillation circuit 30. The oven controlenable data is bit data that enables and disables the oven controlcircuit 40 to operate and is also the action control data on the actionof the oven control circuit 40. The output enable data is bit data thatenables and disables the clock signal output circuit 90 to output theclock signal CLK. The register 82 further stores the frequencyadjustment data for adjustment of the frequency of the clock signal CLKas the control data DCN. The frequency of the clock signal CLK can beset based on the frequency adjustment data at a desired frequencyrequired by an application. For example, when the frequency adjustmentcircuit 92 is formed of a fractional-N-type PLL circuit, the divisionratio data for setting the division ratio that serves as the referenceof the PLL circuit is stored as the frequency adjustment data in theregister 82.

The RAM 84 stores temperature compensation coefficient data used toperform the temperature compensation and digital filter coefficient dataused to perform the digital filtering as the digital signal processingdata. The digital signal processing data may contain at least one of thetemperature compensation coefficient data and the digital filtercoefficient data. The temperature compensation coefficient data iscoefficient data for the temperature compensation performed by thedigital signal processing circuit 52 and is also polynomial coefficientdata used when a temperature compensation voltage that compensates thefrequency-temperature characteristics of the resonator 10 isapproximately expressed by a polynomial. For example, when thetemperature compensation voltage is approximately expressed by apolynomial of the fifth degree, data for setting the zeroth-degreecoefficient, the first-degree coefficient, the second-degreecoefficient, the third-degree coefficient, the fourth-degreecoefficient, and the fifth-degree coefficient of the polynomial arestored as the temperature compensation coefficient data in the RAM 84.The degree of the polynomial is not limited to five and may instead befour or smaller or six or greater. The digital filter coefficient datais coefficient data for the digital filtering performed by the digitalsignal processing circuit 52. The digital filter coefficient data may becoefficient data for FIR lowpass filtering or a coefficient data forKalman filtering. The RAM 84 further stores data for neural networking.For example, when the digital signal processing circuit 52 estimates thetemperature of the resonator 10 by using neural networking based on theresult of the temperature detection performed by the temperature sensorprovided outside or inside the circuit apparatus 20, data necessary forthe neural networking is stored in the RAM 84. For example, coefficientsfor the neural networking or data for setting the gain or the offset ofthe neural networking are stored.

As described above, in the present embodiment, the digital signalprocessing data stored in the RAM 84 contains at least one of thetemperature compensation coefficient data and the digital filtercoefficient data. For example, the temperature compensation coefficientdata and the digital filter coefficient data are each a large amount ofdata. The RAM 84 has a smaller circuit area than that of the register 82but can store a larger amount of data than the register 82. Therefore,storing the temperature compensation coefficient data and the digitalfilter coefficient data in the RAM 84 as the control data DCNtransferred from the non-volatile memory 70 allows data storage using asmaller circuit area than data storage in the register 82, whereby thescale of the circuit apparatus 20 can be reduced.

FIG. 4 shows an example of the signal waveform that describes the actionof the circuit apparatus 20 according to the present embodiment. Afterthe power source voltage VDD is supplied, and when the power sourcevoltage VDD exceeds power-on reset cancellation threshold voltage at atiming t1, the power-on reset circuit 24 changes the level of thepower-on reset signal XPOR from the level L to the level H. The resetstate of the processing circuit 50 is thus canceled, and the processingcircuit 50 starts operating. When the processing circuit 50 makes theoscillation start signal STOS active, the oscillation circuit 30 startsthe oscillation action.

An initial register value has been set in the register 82 at the timingt1, when the reset state is canceled. For example, after the powersource voltage VDD is supplied, the register value held in the register82 is set at the initial value. Specifically, out of the plurality offlipflop circuits that form the register 82, the reset terminal of aflipflop circuit that stores “0” as the initial value is set to beactive, and the set terminal of a flipflop circuit that stores “1” asthe initial value is set to be active. The register value held by theplurality of flipflop circuits is thus set at the initial value. Whenthe register value of the register 82 is set at the initial value, avariety of set values in the circuit apparatus 20 that are set by theregister value are also set at initial values. That is, the voltagelevels of a variety of setting signals set by the register value of theregister 82 are set at voltage levels corresponding to the initialregister value. Each of the circuits of the circuit apparatus 20 thusoperate in accordance with the initial register value. For example, theoscillation action start signal STOS shown in FIG. 2 has an activevoltage level based on the initial register value, and the oscillationaction of the oscillation circuit 30 is enabled. The oscillation circuit30 thus starts the oscillation action after the power source voltage VDDis supplied. On the other hand, the output of the clock signal CLK fromthe clock signal output circuit 90 is disabled based on the initialregister value, and the clock signal CLK is not outputted immediatelyafter the power source voltage VDD is supplied.

As described above, in the present embodiment, an initial value is setin the register 82 after the power source voltage VDD is supplied. Inthe period after the power source voltage VDD is supplied but before thecontrol data DCN is transferred from the non-volatile memory 70 to theholding circuit 80, the oscillation action of the oscillation circuit 30is enabled based on the action control data set as the initial value inthe register 82. In this way, after the power source voltage VDD issupplied, the oscillation action of the oscillation circuit 30 isenabled based on the action control data set as the initial value in theregister 82, and the oscillation action is allowed to start. Thereafter,for example, an action clock signal based on the oscillation signal OSCKfrom the oscillation circuit 30 is used to allow each of the circuits ofthe circuit apparatus 20 to operate. For example, the action clocksignal based on the oscillation signal OSCK allows the processingcircuit 50 to operate to achieve the transfer of the control data DCNfrom the non-volatile memory 70 to the holding circuit 80.

When the oscillation circuit 30 starts the oscillation action, theamplitude detection circuit 22 detects the amplitude of the oscillationsignal OSCK. Thereafter, when the amplitude detection circuit 22 detectsthat the amplitude of the oscillation signal OSCK exceeds thepredetermined value, which is a predetermined voltage, at a timing t2,the level of the detection signal DET changes from the level L to thelevel H. That is, the level of the detection signal DET becomes theactive voltage level. When the detection signal DET becomes active, theprocessing circuit 50 having received the detection signal DET makes thetransfer start signal TSTA active and starts the transfer of the controldata DCN from the non-volatile memory 70 to the holding circuit 80.Specifically, the transfer of the control data DCN from the non-volatilememory 70 to the holding circuit 80 first starts, and the register 82then holds a register value corresponding to the control data DCN.Thereafter, when the transfer to the register 82 is completed, as shownat a timing t3, the transfer of the control data DCN from thenon-volatile memory 70 to the RAM 84 of the holding circuit 80 starts,and the RAM 84 thus holds a RAM value corresponding to the control dataDCN.

As described above, in the present embodiment, the circuit apparatus 20includes the amplitude detection circuit 22, which detects the amplitudeof the oscillation signal OSCK from the oscillation circuit 30. Afterthe action of the oscillation circuit 30 is enabled, the amplitudedetection circuit 22 detects whether or not the amplitude of theoscillation signal OSCK has exceeded the predetermined value. Forexample, after the power source voltage VDD is supplied, the oscillationcircuit 30 starts the oscillation action, and the amplitude detectioncircuit 22 detects whether or not the amplitude of the oscillationsignal OSCK has exceeded the predetermined value. When the amplitudedetection circuit 22 detects that the amplitude of the oscillationsignal OSCK has exceeded the predetermined value, as shown at the timingt2 in FIG. 4, the processing circuit 50 starts transferring the controldata DCN from the non-volatile memory 70 to the holding circuit 80. Forexample, in FIG. 4, the transfer of the control data DCN from thenon-volatile memory 70 to the register 82 first starts, and when thetransfer is completed, the transfer of the control data DCN from thenon-volatile memory 70 to the RAM 84 starts. In this way, the transferof the control data DCN is allowed to start after the amplitude of theoscillation signal OSCK becomes a proper level.

For example, when the oscillation signal OSCK does not reach asufficiently high amplitude level, the action clock signal based on theoscillation signal OSCK undesirably has narrow pulses, which could causemalfunction of the processing circuit 50 and other circuits. Forexample, an error of transfer of the control data DCN and other problemsundesirably occur. In this regard, in the present embodiment, thetransfer of the control data DCN starts after the amplitude of theoscillation signal OSCK exceeds the predetermined value, as shown at thetiming t2 in FIG. 4. Occurrence of the error of transfer of the controldata DCN due to the narrow pulses resulting from an insufficientamplitude level of the oscillation signal OSCK can therefore be avoided.

When the transfer of the control data DCN from the non-volatile memory70 to the holding circuit 80 is completed, the processing circuit 50changes the level of the data transfer end signal TEND from the level Lto the level H to achieve an active voltage level, as shown at a timingt4. The processing circuit 50 then changes the level of the oven controlstart signal STOV from the level L to the level H, which is the activevoltage level. The oven control circuit 40 thus starts the oven controland outputs the oven control signal VOV, which is an oven controlvoltage output signal, to the heater 2. The oven control circuit 40 thusstarts controlling the heater 2. Further, the digital signal processingcircuit 52 of the processing circuit 50 starts the digital signalprocessing, such as the temperature compensation, based on the digitalsignal processing data set by the RAM value of the RAM 84. Atemperature-compensated clock signal CLK is thus outputted from thecircuit apparatus 20.

FIG. 5 describes detailed actions in the present embodiment. In thepresent embodiment, the processing circuit 50 includes the transfercontrol circuit 56, which controls the transfer from the non-volatilememory 70, and the activation control circuit 54, which controls theactivation of the oven control circuit 40, as shown in FIGS. 2 and 5.After the power source voltage VDD is supplied, the transfer controlcircuit 56 instructs the transfer of the control data DCN from thenon-volatile memory 70 to the holding circuit 80. For example, thetransfer control circuit 56 makes the transfer start signal TSTA activeto instruct the non-volatile memory 70 to transfer the control data DCN.Specifically, the transfer control circuit 56, to which the detectionsignal DET has been inputted from the amplitude detection circuit 22,makes the transfer start signal TSTA active when the detection signalDET becomes active to instruct start of the transfer of the control dataDCN. More specifically, the power-on reset signal XPOR has been inputtedfrom the power-on reset circuit 24 to the transfer control circuit 56.After the level of the power-on reset signal XPOR changes to the level Hso that the reset state of the processing circuit 50 is canceled, whenthe detection signal DET becomes active, the transfer control circuit 56makes the transfer start signal TSTA active to instruct start of thetransfer of the control data DCN. In this way, after the oscillationcircuit 30 starts the oscillation action, and when the amplitudedetection circuit 22 detects that the amplitude of the oscillationsignal OSCK has exceeded the predetermined value, the transfer controlcircuit 56 can start transferring the control data DCN from thenon-volatile memory 70 to the holding circuit 80, as shown at the timingt2 in FIG. 4. After the transfer of the control data DCN is completed,the transfer control circuit 56 outputs the data transfer end signalTEND to the activation control circuit 54 to start the action of theoven control circuit 40. That is, when the data transfer end signal TENDis made active, the activation control circuit 54 makes the oven controlstart signal STOV active, and the oven control circuit 40 havingreceived the start signal STOV starts the oven control performed on theheater 2.

In this way, after the power source voltage VDD is supplied, thetransfer control circuit 56 is used to instruct the transfer of thecontrol data DCN, and when the transfer is completed, the transfercontrol circuit 56 outputs the data transfer end signal TEND to theactivation control circuit 54, whereby the activation control circuit 54can be used to cause the oven control circuit 40 to start operating.Therefore, after the power source voltage VDD is supplied, the transferof the control data DCN from the non-volatile memory 70 to the holdingcircuit 80 starts, and after the transfer is completed, the oven controlcircuit 40 can start the oven control. The situation in which the powersource voltage VDD is unstable due to an abrupt increase in the currentconsumed by the heater 2 to cause a data transfer error and otherproblems can therefore be effectively avoided.

Further, the activation control circuit 54 performs the activationcontrol that causes the oven control circuit 40 to start operating whenan oven control enable signal ENOV set by the control data in theholding circuit 80 is active and the data transfer end signal TEND isactive. For example, the oven control enable signal ENOV is set by theregister value of the register 82, as shown in FIG. 3. The registerinitial value is so set that an oven control enable bit is active, sothat the oven control starts after the power source voltage VDD issupplied. Therefore, after the power source voltage VDD is supplied, theoven control enable signal ENOV set by the register value of theregister 82 of the holding circuit 80 becomes active. However, theactivation control circuit 54 does not make the oven control startsignal STOV active even when the oven control enable signal ENOV isactive but unless the data transfer end signal TEND becomes active. Whenthe oven control enable signal ENOV is active, and when the datatransfer end signal TEND becomes active, the activation control circuit54 makes the oven control start signal STOV active to cause the ovencontrol circuit 40 to start operating, as shown at the timing t4 in FIG.4. In this way, after the power source voltage VDD is supplied, the ovencontrol circuit 40 waits for the completion of the transfer of thecontrol data DCN from the non-volatile memory 70 to the holding circuit80 and is then allowed to start operating. The situation in which thepower source voltage VDD is unstable due to an abrupt increase in thecurrent consumed by the heater 2 to cause a data transfer error andother problems can therefore be effectively avoided.

2. Oven Control Circuit, Heater 2

FIG. 6 shows an example of the configuration of the oven control circuit40. The oven control circuit 40 includes an operational amplifier OPA, acurrent source IBA, and resistors RA1 and RA2. A temperature sensor 3 isa temperature detection device for oven control and is provided in theoscillator 4. Specifically, the temperature sensor 3 is provided alongwith the resonator 10 in the thermostatic chamber. In FIG. 6, thetemperature sensor 3 is achieved by diodes. That is, the temperaturesensor 3 is achieved by PN junctions. The temperature sensor 3 iscoupled to the oven control circuit 40 via a pad T7, which is aconnection terminal. The current source IBA supplies the temperaturesensor 3 with a bias current via the pad T7, and a voltage VA2 in theforward direction of the diodes is inputted to the oven control circuit40 via the pad T7. The current source IBA can be achieved, for example,by a current mirror circuit.

The operational amplifier OPA, the resistors RA1 and RA2, a resistorRA3, and a capacitor CA form an integration circuit. The integrationcircuit is a PI control circuit (Proportional-Integral Controller). Theresistor RA3 and the capacitor CA are a feedback resistor and a feedbackcapacitor of the integration circuit, respectively, and are coupled inparallel to each other between pads T8 and T9. The voltage VA2 at thepad T7 and a voltage VA1 at the pad T8 are so controlled as to be equalto each other via an imaginary short circuit of the operationalamplifier OPA. When the voltage VA2 in the forward direction of thediodes, which form the temperature sensor 3, changes, the operationalamplifier OPA operates in such a way that the voltage VA2 is equal tothe voltage VA1 at the pad T8 to produce the oven control signal VOV.The resistors RA1 and RA2 are each a variable resistor, and the variableresistance values thereof set the oven temperature.

The oven control signal VOV produced by the oven control circuit 40 isoutputted via the pad T3, which is an output terminal, to the heater 2provided in the oscillator 4. The heater 2 includes a heater transistorTB, which is a heat generator. The heater transistor TB is, for example,a heat generating MOS transistor. The oven control signal VOV controlsthe voltage at the gate of the heater transistor TB, whereby the heatgeneration performed by the heater 2 is controlled.

The temperature sensor 3 and the heater 2 for the oven control may beformed of a heater IC1, which is a single semiconductor chip, as shownin FIG. 6. The temperature sensor 3 and the oven control circuit 40 donot necessarily have the configurations shown in FIG. 6. For example, athermistor may be used as the temperature sensor 3. The heatertransistor for the heater 2 may be a heat generating bipolar transistorin place of a heat generating MOS transistor. The heater 2 may insteadbe achieved by a Peltier device or a heat generating resistor.

FIG. 7 shows an example of the configuration of the heater 2. The heater2 includes the heater transistor TB and resistors RB1 and RB2. When theoven control signal VOV is inputted to the gate of the heater transistorTB, a current flows through the resistor RB1 and the heater transistorTB. The heater 2 thus generates heat. Further, providing the resistorRB2, which is a pull-down resistor, between the gate node of the heatertransistor TB and GND allows the gate node to be pulled down to GND. Asa result, in a period before the oven control circuit 40 activates theoven control, the heater transistor TB can be turned off so that nocurrent flows therethrough.

FIG. 8 shows an example of the configuration of the operationalamplifier OPA. The operational amplifier OPA includes a differentialsection formed of transistors TC1, TC2, TC3, TC4, and TC5 and an outputsection formed of transistors TC6 and TC7. The transistors TC1 and TC2form a current mirror circuit, and the voltages VA1 and VA2 are inputtedto the gates of the transistors TC3 and TC4, which form a differentialpair. A vias voltage VBS is inputted to the gates of the transistors TC5and TC7, which serve as a vias current source. The oven control startsignal STOV is inputted to the gate of a transistor TC8, and anegative-logic oven control start signal XSTOV is inputted to the gatesof transistors TC9 and TC10. Therefore, when the level of the startsignal STOV becomes the level L before the start of the oven control, anoutput node NC1 of the differential section of the operational amplifierOPA is pulled up, and when the level of the start signal XSTOV becomesthe level H, a bias node NC2 of the bias voltage VBS and an output nodeNC3 of the operational amplifier OPA are pulled down. The action of theoperational amplifier OPA is thus disabled, and the action of the ovencontrol circuit 40 is also disabled. The oven control then starts, andwhen the levels of the start signals STOV and XSTOV become the level Hand the level L, respectively, the transistors TC8, TC9, and TC10 areturned off, so that the pulled-up and pulled-down states described aboveare canceled. The operational amplifier OPA is therefore so set as tooperate in the normal action state, whereby the oven control circuit 40performs appropriate oven control.

3. Oscillator

FIG. 9 shows an example of the structure of the oscillator 4 accordingto the present embodiment. The oscillator 4 includes the resonator 10,the circuit apparatus 20, and a package 5, which accommodates theresonator 10 and the circuit apparatus 20. The package 5 is made, forexample, of a ceramic material and has a hermetically sealedaccommodation space SP1 therein. Specifically, the package 5 is formedof a substrate 6 and an enclosure 7, which is so provided as to form theaccommodation space SP1 between the substrate 6 and the enclosure 7.External connection terminals for coupling the oscillator 4 to anexternal device are formed on the outer bottom surface of the substrate6. The external connection terminals are, for example, VDD, GND, and CLKterminals.

A container 15, which forms the thermostat chamber, is provided in theaccommodation space SP1 of the package 5. The container 15 is formed ofa base 16 and a lid 17, which is so provided as to form an accommodationspace SP2 between the base 16 and the lid 17. The resonator 10, thecircuit apparatus 20, and the heater 2 are provided in the accommodationspace SP2 formed by the base 16 and the lid 17. The base 16 of thecontainer 15 is supported by supports 12 and 13, which are provided onthe inner bottom surface of the substrate 6 of the package 5.

A stepped section 18 is provided in the base 16 of the container 15, andthe heater 2 is disposed in the stepped section 18. Specifically, theheater IC1 shown in FIG. 6 is disposed as the heater 2. The temperaturesensor 3 can thus be disposed in the thermostat chamber, which is theaccommodation space SP2 of the container 15. A temperature sensorseparate from the heater 2 may be disposed in the thermostat chamber.

The resonator 10 is supported by the stepped section 18 via the heater2. The circuit apparatus 20 is disposed below the resonator 10. The term“below” corresponds to the direction from the enclosure 7 of the package5 toward the substrate 6 thereof. Specifically, the circuit apparatus20, which is a semiconductor chip, is disposed in a recess in the innerbottom surface of the base 16. A circuit part 14 is provided on theouter bottom surface of the base 16. The circuit part 14 is, forexample, a capacitor, a resistor, or a temperature sensor. The resonator10 and the circuit apparatus 20 are electrically coupled to each otherby using internal wiring lines, terminal electrodes, or electricallyconductive bumps.

4. Electric Instrument and Vehicle

FIG. 10 shows an example of the configuration of an electric instrument500 including the circuit apparatus according to the present embodiment.The electric instrument 500 includes the circuit apparatus 20 accordingto the present embodiment and a processing apparatus 520, which operatesin accordance with the clock signal CLK based on the oscillation signalOSCK from the oscillation circuit 30 of the circuit apparatus 20.Specifically, the electric instrument 500 includes the oscillator 4including the circuit apparatus 20 according to the present embodiment,and the processing apparatus 520 operates based on the clock signal CLKfrom the oscillator 4. The electric instrument 500 can further includean antenna ANT, a communication interface 510, an operation interface530, a display section 540, and a memory 550. The electric instrument500 does not necessarily have the configuration shown in FIG. 10, and avariety of variations are conceivable, that is, part of the componentsin the configuration can be omitted, or another component can be addedto the configuration.

The electric instrument 500 is, for example, a network-relatedinstrument, such as a base station and a router, a high-precisionmeasurement instrument that measures a physical quantity, such as adistance, a time period, a flow speed, and a flow rate, a biologicalinformation measurement instrument that measures biological information,or an in-vehicle instrument. The biological information measurementinstrument is, for example, an ultrasonic measurement apparatus, a pulsewave meter, and a blood pressure measurement apparatus. The in-vehicleinstrument is, for example, an instrument for automatic driving. Theelectric instrument 500 may instead be a wearable instrument, such as ahead mounted display and a timepiece-related instrument, a robot, aprinting apparatus, a projection apparatus, a portable informationterminal, such as a smartphone, a content providing instrument thatdistributes a content, and a video instrument, such as a digital cameraand a video camcorder.

The electric instrument 500 may still instead be an instrument used in anext-generation mobile communication system, such as a 5G mobilecommunication system. For example, the circuit apparatus 20 according tothe present embodiment can be used in a variety of instruments, such asa base station of a next-generation mobile communication system, aremote radio head (RRH), or a mobile communication terminal. Anext-generation mobile communication system requires a high-precisionclock frequency, for example, for time synchronization and is suitablefor an application of the circuit apparatus 20 according to the presentembodiment capable of producing the high-precision clock signal CLK.

The communication interface 510 receives data from an external componentand transmits data to the external component via the antenna ANT. Theprocessing apparatus 520, which is a processor, controls the electricinstrument 500 and performs a variety of digital processing on the datatransmitted and received via the communication interface 510. Thefunctions of the processing apparatus 520 can be achieved, for example,by a microcomputer or any other processor. The operation interface 530allows a user to perform input operation and can be achieved, forexample, by operation buttons or a touch panel display. The displaysection 540 displays a variety of types of information and can beachieved, for example, by a display based on a liquid crystal or organicEL material. The memory 550 stores data, and the functions of the memory550 can be achieved, for example, by a semiconductor memory, such as aRAM and a ROM.

FIG. 11 shows an example of a vehicle including the circuit apparatus 20according to the present embodiment. The vehicle includes the circuitapparatus 20 according to the present embodiment and a processingapparatus 220, which operates in accordance with the clock signal CLKbased on the oscillation signal OSCK from the oscillation circuit 30 ofthe circuit apparatus 20. Specifically, the vehicle includes theoscillator 4 including the circuit apparatus 20 according to the presentembodiment, and the processing apparatus 220 operates based on the clocksignal CLK from the oscillator 4. The circuit apparatus 20 according tothe present embodiment can be incorporated into a variety of vehicles,for example, a car, an airplane, a motorcycle, a bicycle, or a ship. Thevehicle is, for example, any of instruments and apparatuses that includean engine, a motor, or any other drive mechanism, a steering wheel, arudder, or any other steering mechanism, and a variety of electronicinstruments and travel on the ground, in the sky, or on the sea. FIG. 11schematically shows an automobile 206 as a specific example of thevehicle. The automobile 206 incorporates the circuit apparatus 20according to the present embodiment. Specifically, the automobile 206,which is a vehicle, includes a control apparatus 208, and the controlapparatus 208 includes the oscillator 4 including the circuit apparatus20 according to the present embodiment, and the processing apparatus220, which operates based on the clock signal CLK produced by theoscillator 4. The control apparatus 208, for example, controls thedegree of hardness of the suspension in accordance with the posture of avehicle body 207 and performs braking control on individual wheels 209.For example, the control apparatus 208 may achieve automatic driving ofthe automobile 206. An instrument that incorporates the circuitapparatus 20 according to the present embodiment is not necessarily thecontrol apparatus 208, and the circuit apparatus 20 can be incorporatedin a variety of in-vehicle instruments, such as a meter panel instrumentand a navigation instrument provided in a vehicle, such as theautomobile 206.

As described above, the circuit apparatus according to the presentembodiment includes an oscillation circuit that causes a resonator tooscillate to produce an oscillation signal, an oven control circuit thatcontrols a heater provided in correspondence with the resonator, anon-volatile memory that stores control data, a holding circuit thatholds the control data transferred from the non-volatile memory, and aprocessing circuit that carries out a process based on the control dataheld in the holding circuit. After a power source voltage is supplied,the processing circuit carries out the process of transferring thecontrol data from the non-volatile memory to the holding circuit, andafter the transfer of the control data is completed, the processingcircuit causes based on a data transfer end signal the oven controlcircuit to start operating.

According to the present embodiment, the oscillation circuit causes theresonator to oscillate to produce the oscillation signal, and the ovencontrol circuit controls the heater provided in correspondence with theresonator. The non-volatile memory stores the control data, the holdingcircuit holds the control data transferred from the non-volatile memory,and the processing circuit carries out a process based on the heldcontrol data. According to the present embodiment, after the powersource voltage is supplied, the control data is transferred from thenon-volatile memory to the holding circuit, and after the transfer ofthe control data is completed, the oven control circuit startsoperating. As described above, in the present embodiment, the ovencontrol circuit does not start operating immediately after the powersource voltage is supplied, but the control data is transferred from thenon-volatile memory to the holding circuit before the oven controlcircuit starts operating. After the transfer of the control data iscompleted, the oven control circuit starts controlling the heater. Inthis way, the oven control circuit does not start operating in the datatransfer period in which the control data is transferred from thenon-volatile memory to the holding circuit, so that no oven control inwhich the heater is controlled is performed. The situation in which anunstable power source voltage in the data transfer period causesincorrect control data to be transferred to the holding circuit andother troubles can therefore be suppressed.

In the present embodiment, the processing circuit may include a digitalsignal processing circuit that performs digital signal processingincluding temperature compensation performed on the oscillationfrequency of the resonator. The control data may include action controldata for controlling the action of the oscillation circuit and digitalsignal processing data used in the digital signal processing. Theholding circuit may include a register that holds the action controldata and a RAM that holds the digital signal processing data.

The oscillation circuit can thus be so controlled as to start theoscillation action by using the action control data, which is controldata on the action of the oscillation circuit and which is transferredfrom the non-volatile memory to the register. After the oscillationcircuit thus starts the oscillation action using the resonator andproduces the oscillation signal, the digital signal processing datatransferred from the non-volatile memory to the register can be used toallow the digital signal processing circuit to perform the digitalsignal processing.

In the present embodiment, the digital signal processing data maycontain at least one of temperature compensation coefficient data usedin the temperature compensation and digital filter coefficient data usedin digital filtering.

Storing at least one of the temperature compensation coefficient dataand the digital filter coefficient data in the RAM as the digital signalprocessing data and as the control data transferred from thenon-volatile memory as described above allows data storage using asmaller circuit area than data storage in the register, whereby thescale of the circuit apparatus can be reduced.

In the present embodiment, an initial value may be set in the registerafter the power source voltage is supplied, and in the period after thepower source voltage is supplied but before the control data istransferred from the non-volatile memory to the holding circuit, theoscillation action of the oscillation circuit may be enabled based onthe action control data set as the initial value in the register.

In this way, after the power source voltage is supplied, the oscillationaction of the oscillation circuit is enabled based on the action controldata set as the initial value in the register, and the oscillationaction is allowed to start.

In the present embodiment, the circuit apparatus may include anamplitude detection circuit that detects the amplitude of theoscillation signal. After the action of the oscillation circuit isenabled, and when the amplitude detection circuit detects that theamplitude of the oscillation signal has exceeded a predetermined value,the processing circuit may start transferring the control data from thenon-volatile memory to the holding circuit.

In this way, the transfer of the control data is allowed to startprovided that the amplitude of the oscillation signal becomes a properlevel after the action of the oscillation circuit is enabled, wherebyappropriate data transfer can be achieved.

In the present embodiment, the circuit apparatus may include anamplitude detection circuit that detects the amplitude of theoscillation signal. After the power source voltage is supplied, theoscillation circuit starts the oscillation action, and when theamplitude detection circuit detects that the amplitude of theoscillation signal exceeds a predetermined value, the processing circuitmay start transferring the control data from the non-volatile memory tothe holding circuit.

In this way, the transfer of the control data is allowed to startprovided that the amplitude of the oscillation signal becomes a properlevel after the power source voltage is supplied and the oscillationcircuit starts the oscillation action, whereby appropriate data transfercan be achieved.

In the present embodiment, the processing circuit may include a transfercontrol circuit that controls the transfer from the non-volatile memoryand an activation control circuit that controls the activation of theoven control circuit. After the power source voltage is supplied, thetransfer control circuit may instruct the transfer of the control datafrom the non-volatile memory to the holding circuit, and after thetransfer of the control data is completed, the transfer control circuitmay output a data transfer end signal to the activation control circuitto cause the oven control circuit to start operating.

In this way, after the power source voltage is supplied, the transfercontrol circuit is used to instruct the transfer of the control data,and when the transfer is completed, the transfer control circuit outputsthe data transfer end signal to the activation control circuit, wherebythe activation control circuit can be used to cause the oven controlcircuit to start operating.

In the present embodiment, the activation control circuit may cause theoven control circuit to start operating when an oven control enablesignal set by the control data in the holding circuit is active and thedata transfer end signal is active.

In this way, also when the oven control enable signal is set to beactive, the oven control circuit does not start operating immediatelyafter the power source voltage is supplied, and the oven control circuitwaits for the completion of the transfer of the control data from thenon-volatile memory to the holding circuit and is then allowed to startoperating.

The present embodiment further relates to an oscillator including thecircuit apparatus described above, the resonator, and a heater.

The present embodiment further relates to an electronic instrumentincluding the circuit apparatus described above and a processingapparatus that operates in accordance with a clock signal based on theoscillation signal.

The present embodiment further relates to a vehicle including thecircuit apparatus described above and a processing apparatus thatoperates in accordance with a clock signal based on the oscillationsignal.

The present embodiment has been described above in detail, and a personskilled in the art will readily appreciate that a large number ofvariations are conceivable to the extent that they do not substantiallydepart from the novel items and effects of the present disclosure. Suchvariations are all therefore assumed to fall within the scope of thepresent disclosure. For example, a term described at least once in thespecification or the drawings along with a different term having aboarder meaning or the same meaning can be replaced with the differentterm anywhere in the specification or the drawings. Further, anycombination of the present embodiment and the variations fall within thescope of the present disclosure. Moreover, the configuration, action,and other factors of each of the circuit apparatus, the oscillator, theelectronic instrument, and the vehicle are not limited to thosedescribed in the present embodiment, and a variety of changes can bemade thereto.

What is claimed is:
 1. A circuit apparatus comprising: an oscillationcircuit that causes a resonator to oscillate to produce an oscillationsignal; an oven control circuit that controls a heater provided incorrespondence with the resonator; a non-volatile memory that storescontrol data; a holding circuit that holds the control data transferredfrom the non-volatile memory; and a processing circuit that carries outa process based on the control data held in the holding circuit, whereinafter a power source voltage is supplied, the processing circuit carriesout the process of transferring the control data from the non-volatilememory to the holding circuit, and after the transfer of the controldata is completed, the processing circuit causes, based on a datatransfer end signal, the oven control circuit to start operating,wherein the processing circuit includes a transfer control circuit thatcontrols the transfer from the non-volatile memory and an activationcontrol circuit that controls the activation of the oven controlcircuit, and after the power source voltage is supplied, the transfercontrol circuit instructs the transfer of the control data from thenon-volatile memory to the holding circuit, and after the transfer ofthe control data is completed, the transfer control circuit outputs adata transfer end signal to the activation control circuit to cause theoven control circuit to start operating.
 2. The circuit apparatusaccording to claim 1, wherein the processing circuit includes a digitalsignal processing circuit that performs digital signal processingincluding temperature compensation performed on an oscillation frequencyof the resonator, the control data includes action control data forcontrolling the action of the oscillation circuit and digital signalprocessing data used in the digital signal processing, and the holdingcircuit includes a register that holds the action control data and a RAMthat holds the digital signal processing data.
 3. The circuit apparatusaccording to claim 2, wherein the digital signal processing datacontains at least one of temperature compensation coefficient data usedin the temperature compensation and digital filter coefficient data usedin digital filtering.
 4. The circuit apparatus according to claim 2,wherein an initial value is set in the register after the power sourcevoltage is supplied, and in a period after the power source voltage issupplied but before the control data is transferred from thenon-volatile memory to the holding circuit, an oscillation action of theoscillation circuit is enabled based on the action control data set asthe initial value in the register.
 5. The circuit apparatus according toclaim 4, further comprising an amplitude detection circuit that detectsan amplitude of the oscillation signal, wherein after the action of theoscillation circuit is enabled, and when the amplitude detection circuitdetects that the amplitude of the oscillation signal exceeds apredetermined value, the processing circuit starts transferring thecontrol data from the non-volatile memory to the holding circuit.
 6. Thecircuit apparatus according to claim 1, further comprising an amplitudedetection circuit that detects an amplitude of the oscillation signal,wherein after the power source voltage is supplied, the oscillationcircuit starts an oscillation action, and when the amplitude detectioncircuit detects that the amplitude of the oscillation signal exceeds apredetermined value, the processing circuit starts transferring thecontrol data from the non-volatile memory to the holding circuit.
 7. Thecircuit apparatus according to claim 1, wherein the activation controlcircuit causes the oven control circuit to start operating when an ovencontrol enable signal set by the control data in the holding circuit isactive and the data transfer end signal is active.
 8. An oscillatorcomprising: the circuit apparatus according to claim 1; the resonator;and a heater.
 9. An electronic instrument comprising: the circuitapparatus according to claim 1; and a processing apparatus that operatesin accordance with a clock signal based on the oscillation signal.
 10. Avehicle comprising: the circuit apparatus according to claim 1; and aprocessing apparatus that operates in accordance with a clock signalbased on the oscillation signal.
 11. A circuit apparatus comprising: anoscillation circuit that causes a resonator to oscillate to produce anoscillation signal; an oven control circuit that controls a heaterprovided in correspondence with the resonator; a non-volatile memorythat stores control data; a holding circuit that holds the control datatransferred from the non-volatile memory; and a processing circuit thatcarries out a process based on the control data held in the holdingcircuit, wherein after a power source voltage is supplied, theprocessing circuit carries out the process of transferring the controldata from the non-volatile memory to the holding circuit, and after thetransfer of the control data is completed, the processing circuitcauses, based on a data transfer end signal, the oven control circuit tostart operating, wherein the processing circuit includes a digitalsignal processing circuit that performs digital signal processingincluding temperature compensation performed on an oscillation frequencyof the resonator, the control data includes action control data forcontrolling the action of the oscillation circuit and digital signalprocessing data used in the digital signal processing, and the holdingcircuit includes a register that holds the action control data and a RAMthat holds the digital signal processing data.
 12. A circuit apparatuscomprising: an oscillation circuit that causes a resonator to oscillateto produce an oscillation signal; an oven control circuit that controlsa heater provided in correspondence with the resonator; a non-volatilememory that stores control data; a holding circuit that holds thecontrol data transferred from the non-volatile memory; a processingcircuit that carries out a process based on the control data held in theholding circuit, wherein after a power source voltage is supplied, theprocessing circuit carries out the process of transferring the controldata from the non-volatile memory to the holding circuit, and after thetransfer of the control data is completed, the processing circuitcauses, based on a data transfer end signal, the oven control circuit tostart operating; and an amplitude detection circuit that detects anamplitude of the oscillation signal, wherein after the power sourcevoltage is supplied, the oscillation circuit starts an oscillationaction, and when the amplitude detection circuit detects that theamplitude of the oscillation signal exceeds a predetermined value, theprocessing circuit starts transferring the control data from thenon-volatile memory to the holding circuit.